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New Scientist Live

Crazy comet ISON returns bearing solar system secrets

By Jacob Aron

COMET ISON is slinking away without putting on the light show it promised, but its scientific legacy will live on. ISON will improve our picture of the early solar system, and might aid the first landing of a probe on a comet.

Named for the International Scientific Optical Network in Russia, where it was discovered, ISON is not living up to its initial “comet of the century” billing. But it is the best-observed comet of the space age, watched by dozens of probes plus hundreds of professional and amateur astronomers. It was pronounced dead after diving through the sun’s atmosphere last week, only to reappear – prompting Karl Battams of the Naval Research Laboratory in Washington DC to dub it “Schrödinger’s comet”.

Comets usually glow brighter after passing the sun, but ISON is rapidly dimming. “It is fairly unlikely to be a naked-eye object,” says Geraint Jones of University College London.

Exactly what remains is not clear. Either the nucleus now resembles a baked Alaska – a burnt crust insulating a core of ice and preventing it from releasing gas that would glow – or, more likely, it has broken up and we are just seeing a fragment.

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Comet ISON’s nucleus may now resemble a baked Alaska – a burnt crust insulating a core of ice

The latter is still interesting. “We’re probably seeing material that was buried deep within the interior of the comet,” says Stephen Lowry of the University of Kent, UK. For more than a million years, ISON has travelled sunward from the distant Oort cloud, which contains material frozen as the solar system formed. The composition of ISON and other comets will yield clues to the distribution of different substances in the early solar system.

ISON could also help the European Space Agency land on comet Churyumov-Gerasimenko next year. Observations of ISON may assist in predicting whether ESA’s Rosetta probe will have to contend with a single body or multiple fragments, says Hermann Böhnhardt of the Max Planck Institute for Solar System Research in Lindau, Germany.

This article appeared in print under the headline “‘Schrödinger’s comet’ leaves a clear legacy”